406 Coupe - loud band from roof

Could be a Marillion concert.

Do you know the history of the car? Has it had any major bodywork repairs? If so it could be that the shell isn't completely straight and what youy are hearing is stress in the shell releasing as the shell warms/cools.

I suggest getting it checked out on a jig.

It could, of course, be caused by something completely different.

Does it only happen with the radio on?

I had what turned out to be a dry joint in the radio that fed the right hand front of the speakers.

At first I thought a stone had been thrown up by another car and hit the windscreen it was so loud. Just like you, it would happen once per journey and would scare the life out of me as it would come out of the blue. In the end, I took the radio out and ran fresh solder around the leads on the pcb that supplied the speakers and the bang disappeared and so far has never returned.

Robin

i'd say Metalica is on your roof

My dad's just been telling me he had this problem once with a van . turned out to be three vans welded together ;-) Thinking about your prob. set me wondering. I had a real big (s*it-yourself) bang one night driving on a country road. It sounded something like a bigish stone hitting the n/s window or door. At the time I assumed it had to be some prat chucking stones about. Mysterious eh!